Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$211.69	6.716%	$225.9071	$225.91	$225.90	$225.90
Purchase #2	$186.90	7.622%	$201.1455	$201.15	$201.15	$201.10
Purchase #3	$200.34	10.526%	$221.4278	$221.43	$221.45	$221.40
Purchase #4	$53.26	11.322%	$59.2901	$59.29	$59.30	$59.30
Purchase #5	$83.41	3.642%	$86.4478	$86.45	$86.45	$86.40
Purchase #6	$157.71	6.208%	$167.5006	$167.50	$167.50	$167.50
Purchase #7	$119.71	6.850%	$127.9101	$127.91	$127.90	$127.90
7 purchase totals =	$1,013.02		$1,089.6290	$1,089.64	$1,089.65	$1,089.50